Cloning Variation Studied

Technique Holds Controversial Promise For Same-sex Couples

Scientists are studying a variation on cloning that -- if it works -- could lead to a new treatment for infertility and give same-sex couples the ability to create babies that share their DNA.

While cloning creates the mirror image of donors who supply their DNA, the new technique, known as haploidization, seeks to prompt DNA from a simple skin cell to take on the role of either a sperm or egg cell. In theory at least, these artificially created sex cells could create an embryo from the DNA from two males, or from two females.

Preliminary data that support the concept met with skepticism Tuesday when it was presented in Seattle at the annual meeting for the American Society for Reproductive Medicine, said Xiangzhong ``Jerry'' Yang of the University of Connecticut, who worked on the technique with scientists in Brazil.

Yang noted that the technique has yet to produce a pregnancy, much less an animal.

``We want to demonstrate whether it works or not,'' he said.

However, Yang said, the work has potential. It could help infertile couples who want to have children who would have both parental sets of genes. And it should help scientists better understand the function of genes in disease.

Yang acknowledged that the technique's potential to help gay couples have babies carrying both parents' genes might prove controversial.

``Cloning created an ethical debate, and I am sure that this will be the case here, too,'' Yang said. ``This needs to be the subject of societal debate. But we hope that it doesn't interfere with fundamental research.''

In cloning, DNA from skin or other non-sex cells is placed into an egg stripped of its own DNA. When the egg is stimulated, an embryo is created that contains only genetic material from the donor of the skin cell.

So an individual produced through cloning is the genetic twin of the skin cell donor.

Haploidization uses cloning techniques, but its ultimate goal is to combine two sources of genetic material, just as occurs when a sperm fertilizes an egg.

To accomplish this goal, the skin cell --or other adult cell -- must become a gamete or sex cell, which has half the normal complement of chromosomes of an adult cell.

Under the new technique, the DNA from a donor cell could play the role of sperm and combine with DNA of an egg. Conversely, a sperm could fertilize an egg that has had its own DNA replaced with that from a donor skin cell.

Yang calls this process the creation of ``artificial gametes'' or sex cells.

However, the paper submitted in Seattle by Yang and Dr. Peter Nagy, an embryologist in Sao Paulo, describes only the first tentative steps toward that goal.

Yang and Nagy recounted how they transferred the nuclei from the skin cells of a mouse into an immature mouse egg that was in the process of reducing the number of chromosomes, or becoming ``haploid'' and ready for fertilization. The mouse egg with the implanted DNA eventually was coaxed into beginning cell divisions, and researchers found that the egg contained two ``haploid'' nuclei, or cells with appropriate complement of chromosomes. If such eggs were fertilized with sperm, in theory, Yang said, they should create an embryo containing DNA from both the skin cell and the sperm.

``It suggests that the skin cells became sex-like cells,'' Yang said. ``And that opens up some fundamental questions in biology.''

Yang said the most obvious application of the technology would be to aid an older woman who cannot become pregnant because of the poor quality of her eggs. A fertility clinic might remove DNA from a donor egg and replace it with DNA from a woman's skin cell. The egg then could be fertilized by her husband's sperm, allowing the couple to have a baby who would share both parents' genes, instead of those of the father and a female egg donor.